For ease of understanding, the invention will be described in terms of its application as a compressor.
Rotary vane compressors of the type in which a rotor, which carries a plurality of extensible and retractable vanes, rotates in a housing about an axis which is radially displaced from the axis of the housing bore are well-known. These compressors have many uses and literally thousands are put into service each year. Because of competitive pressure it is desirable to lower the weight and the cost of manufacturing such compressors. One expedient is to fabricate some of the compressor components of die cast aluminum. This lowers the weight since the conventional compressors are made from cast iron. Various attempts have been made to develop such a compressor including, purely by way of example, the apparatus disclosed in U.S. Pat. No. 3,552,895 which is said to have run for approximately 1,000 hours with no signs of appreciable wear, from which it may be inferred that a significantly greater service use, such as a doubling or tripling of operating time, would result in appreciable wear and therefore termination of useful service life.
The rotary vane compressor of the present invention has run over 8,000 hours under conventional service conditions without evidence of approaching failure and continues to operate. This has been accomplished in a structure which is very cost competitive with conventional compressors of similar rated and actual capacity. These desirable results have been achieved by the judicious use of complementary materials, with each material being appropriately matched to its required function.
In a preferred embodiment of the invention the rotor housing is formed from cast iron and the rotor is formed from either cast iron or by powder metallurgy techniques since either variant will produce acceptable results in the intended environment. The parts which abut the ends of the rotor housing are preferably made from aluminum, with the surfaces of said parts which contact the rotor housing being preferably coated with a suitable plastic material. Such a construction has yielded the impressive campaign results described above.
Two further features contribute to the long life of the compressor of this invention.
As is well known, bearing failure of the rotor shaft is a significant problem in such compressors. A contributing factor to such bearing failure is the fact that, in operation, the air which flows past the mid-plate assembly and along the motorshaft and impinges on the bearing has carbon dust and other particles, some of which are abrasive in nature, entrained therein. These materials, when they come in contact with the shaft bearing, may actually be entrapped in the bearing which effects its operation and, also, the bearing tends to overheat. The air is hot and even though there is no entrapment of the particles in the bearing, both the bearing and its seal are detrimentally affected by the hot air flow. The cumulative effect of prolonged exposure of the bearing to the carbon dust and particle laden air results in bearing failure much earlier than would be the case if these materials were not present in the hot air which impinges directly on the bearing. Accordingly, the deleterious effect of such dust and particles and hot air, said means including a slinger located upstream in the air flow to the bearing. The slinger functions to direct a substantial portion of the dust and particles and hot air away from the bearing, said dust and particles being thereby diverted to a fluid flow path which substantially by-passes the bearing.
As is also well-known, the vanes tend to fail before the balance of the components reach the end of their useful life. A prime cause of failure is the shaving action which the trailing edge of each vane slot in the rotor exerts on its associated vane. This problem appears to be entirely eliminated in the present invention by rounding the peripheral edge of each trailing vane slot with the result that the shaving action is eliminated and vane life dramatically increased.
Accordingly a primary object of the invention is to provide a rotary vane compressor fabricated from conventional materials by conventional methods which has a useful life much greater than the useful life of conventional compressors formed from the same class of materials.
Another object is to provide a rotary vane compressor as above-described which does not require unusual manufacturing techniques or utilize special coatings, such as aluminum oxide coatings.
A further object is to provide a slinger especially adapted for a rotary vane compressor which functions as a baffle to divert a portion of the carbon dust and abrasive particles, which are entrained in the air flow path along the rotor shaft, away from the rotor shaft bearing.
Yet a further object is to provide a rotary vane compressor which includes a slinger which functions as a baffle to divert a portion of the carbon dust and abrasive particles, which are entrained in the air flow path along the rotor shaft, away from the rotor shaft bearing.
Another object is to provide a rotor for a rotary vane compressor which exerts no shaving effect on the individual vanes as they reciprocate in their associated slots in the rotor.
Yet another object is to provide a rotary vane compressor which includes a rotor having means for reducing the shaving of each vane by the rotor as each vane reciprocates in its associated slot.
Other objects and advantages of the invention will become apparent from the following description of a preferred embodiment.